1. Field of the Invention:
The invention relates to a combustion chamber of an internal combustion engine which prevents knocking in operation.
2. Description of the Prior Art:
An engine including cylinders each having a plurality of spark plugs has been known which performs rapid and stable combustion even when it is operated under an exhaust gas recirculation system with a relatively large amount of re-introduced exhaust gas which would cause unstable combustion in an engine including cylinders each having a single spark plug. Such a rapid and stable combustion greatly improves the fuel consumption and driving performance and greatly reduces the generation of nitrous oxides (NOx) in the exhaust gas.
With the conventional engine including cylinders each having two spark plugs, however, combustion chambers are hemispherical or disc-like and spark plugs are symmetrically located with respect to centers of cylinders. With this arrangement, when a higher compression ratio is employed to improve the engine efficiency, hot residual gases of the previous cycle present in the combustion chamber furthest from the spark plugs are insufficiently cooled and cause an extraordinary combustion such as knocking or preignition. To avoid this, the ignition timing must be delayed and deviated from the minimum advance for the best torque (MBT), with the result that the higher compression ratio cannot bring about the desired improved effect.